Mobile devices with built-in cameras have become more popular as inexpensive image sensors, e.g. based on CMOS technology, became available. Particularly, mobile radio telephones (cell phones) and PDA computers (personal digital assistant) are provided with built-in cameras. Images and videos captured through these cameras are stored locally in the mobile devices, off-loaded via device interfaces to personal computers, and/or transferred via mobile radio networks to servers or other mobile devices. Typical applications of mobile communication devices with built-in cameras include video telephony and visual supervision and monitoring of remote objects. Typically, the known applications of mobile devices having built-in cameras are limited to capturing, transferring, storing and/or displaying image (pictorial) data. If there is any further processing of captured image data in the mobile devices, it is limited to extracting information contained in the image data, e.g. a printed article number or a street name.